Year 9 Science · Unit 1 · Lesson 6

Second Line of Defence

Foundation Worksheet

Name

Date

Class

Learning Goals

Match key second-line defence terms to their correct definitions.
Sequence the steps of phagocytosis in the correct order.
Explain the roles of neutrophils and macrophages in fighting infection.

Warm Up

Match each term to its definition

Write the matching letter next to each term in the "Your answer" column.

Term	Your answer	Definition
Inflammation		A. A white blood cell that engulfs and destroys pathogens and debris; arrives after neutrophils; presents antigen fragments to lymphocytes.
Phagocyte		B. The process by which a cell surrounds and engulfs a particle, enclosing it in a membrane-bound vesicle before digesting it with enzymes.
Neutrophil		C. A deliberate increase in core body temperature driven by the hypothalamus; slows pathogen reproduction and enhances immune cell activity.
Macrophage		D. The body's non-specific response to infection or injury, characterised by redness, heat, swelling, and pain as blood flow increases to the site.
Phagocytosis		E. The most abundant white blood cell; a first-responder phagocyte that lives only a few days but can engulf dozens of bacteria.
Fever		F. Any white blood cell specialised in engulfing and destroying foreign particles.

Your Turn

Order the steps

Number the events from 1 to 8 to show the correct order of phagocytosis. Event 1 = what happens first.

Order	Event
	The lysosome fuses with the phagosome, releasing digestive enzymes into the vesicle.
	The pathogen is recognised by receptor proteins on the surface of the phagocyte.
	Enzymes in the phagolysosome digest and destroy the pathogen.
	The pathogen enters the body tissue through a wound or breach.
	The phagocyte extends pseudopods (arm-like projections) around the pathogen.
	Debris from the destroyed pathogen is expelled from the phagocyte.
	The pseudopods close, enclosing the pathogen in a membrane-bound vesicle called a phagosome.
	A neutrophil detects chemical signals (alarm chemicals) released by damaged cells and moves toward the site.

Show What You Know

1. Name the four cardinal signs of inflammation. For each sign, state the biological reason it occurs.

Recall 2 marks

2. Explain why the second line of defence is described as "non-specific." How is this different from the third line of defence (the adaptive immune system)?

Recall 2 marks

Wrap Up

In one sentence, what was the main idea of this lesson?